Biodiversity: when license plates bear witness to the decline of insects

One application, a template on your license plate, and you’re a “citizen scientist”, ready to contribute to an insect decline research. In the UK, two conservation groups, the Kent Wildlife Trust and Buglife, conducted a survey of flying insect populations by asking volunteer motorists to observe the number of insects on their number plates. †

The “Bugs Matter” study compared the data collected in 2021 with a similar study conducted in 2004 by the RSPB (“Royal Society for the Protection of Birds”). The observation is clear: the number of flying insects in the United Kingdom has fallen by 58.5% in 17 years.

Thousands of journeys and more than a million kilometers traveled

Hundreds of “citizen scientists” — as the study authors call them — took part in these participatory observation campaigns conducted between June and August. For 2021, he had to download an application that registers the duration, the distance traveled and the average speed of the trip. After carefully cleaning their license plates before each trip, the volunteers counted the insects on their license plates using a type of stencil called a “splashmeter”, taking into account the area where insects have settled in a homogeneous way. They then entered the information in their application.

The study also took into account the car models, outside temperature and weather, as well as the type of roads taken to harmonize the data. The 2004 study, for example, contains data from nearly 15,000 journeys over approximately 1.4 million kilometres. The 2021 study includes 3,350 journeys over 195,000 kilometers. A third survey was conducted in 2019, although limited to the Kent region.

And if the share of trips where no insects were spotted was 8% in 2004, it will rise to 40% by 2021, the “Guardian” reports. The influence of the aerodynamics of modern cars, which could crush fewer mosquitoes, has been removed from the statistics.

The windshield effect

Scientists from the Kent Wildlife Trust and Buglife say they chose to use cars to observe insects because of the ‘windshield effect’, with motorists seeing fewer and fewer insects on their windshields over the years.

For Philippe Grandcolas, deputy scientific director of the CNRS Ecology and Environment Institute, the data from this British study is “interesting, because if it were necessary to precisely identify insects, it would take a huge device and an army of scientists. “. Despite inaccurate data, the study manages to “answer simple questions” about the variations in insect abundance.

The British authors acknowledge that the current data does not allow to identify a clear trend and want to repeat the experiment every year to clarify the results. For Philippe Grandcolas, “numerous detailed and serious studies” took place in the period not covered by the study. And they all point to the same result: the amount of insects is decreasing.

“It is a massacre with multiple consequences”

“These observations are general and without attraction in environments under human influence. There is a decrease in insect density and the local disappearance of species,” explains Philippe Grandcolas. “In a typical French landscape where human activities take place, we are currently seeing a reduction of more than 60% of the insect density, all species together”. Of the 40,000 species found in France, some are more affected than others, such as those that feed on pollen and nectar, for example. These suffer from the use of pesticides and the decline of floral diversity.

The first cause of insect decline in Europe is the use of pesticides, the CNRS scientist notes. But there is also the decline in land use diversity, which is disrupting habitat and the diversity of places where insects live. Or the extreme events caused by climate change, which disrupt their development and reproduction. Finally: “The introduction of exotic species such as the Asian ladybird or the Asian hornet threatens certain insects. Indeed, they can establish themselves and compete or even replace other varieties present in France,” concludes Philippe Grandcolas.

“It’s a massacre with multiple consequences,” the researcher says bluntly. Indeed, insects are essential to our ecosystems, especially in their role as pollinators. “Without them, life on Earth would collapse,” summarizes the Kent Wildlife Trust. The results of the British study are therefore an opportunity for this organization to sound the alarm. The Kent Wildlife Trust is calling on both governments and private individuals to intervene: using less pesticides and growing grass in your garden for longer already contributes to the building, the organization recalls.

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